JP2822568B2 - On-screen circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing circuit for a television receiver, and more particularly, to channel switching, volume switching, television (TV) /
The present invention relates to an on-screen circuit that performs processing for displaying information such as video switching on a CRT screen (on-screen display).

[Conventional technology]

When information such as channel switching, volume switching, and TV / video switching is displayed on a CRT screen in a television receiver, a digital signal (hereinafter, referred to as an on-screen signal) including such information is transmitted on an on-screen display. Necessary processing is performed by an on-screen circuit having processing functions such as extraction, insertion, and level adjustment of signals required for this.

FIG. 6 is a block diagram of a conventional example of an on-screen circuit.

The on-screen four-circuit 200 of this conventional example has terminals to which primary color signals (R, G, B) from the video signal processing circuit 100 are input.
18a, 18b, 18c and on-screen signal input terminal 2
1a, 21b, 21c, an output terminal 19a, 19b, 19c for sending an output signal in which an on-screen signal is inserted into a primary color signal, and an output level adjustment signal for adjusting the level of the on-screen signal in the output signal. And a terminal 22 for inputting.

[Problems to be solved by the invention]

The above-described conventional on-screen circuit has a disadvantage that the number of pins of the IC is large since the output level adjusting terminal for the on-screen signal is provided independently.

[Means for solving the problem]

The on-screen circuit of the present invention receives an on-screen signal including information such as channel switching, volume switching, television / video switching and the like in a television receiver and a primary color signal supplied from a video signal processing circuit. An on-screen circuit capable of inserting the output on-screen signal into the primary color signal and outputting the adjusted on-screen signal, and adjusting the level of the inserted on-screen signal. A switching means for turning off, a current supply means for supplying a predetermined current via the switching means when the switching means is turned on, and an adjustable current value of the predetermined current; Level, the switching means is turned on, and a predetermined current is supplied from the current supply means. Once supplied, to generate a voltage corresponding to the predetermined current, and having a means for inserting the generated voltage to the primary color signals.

[Action]

By making the current value flowing when the on-screen signal (digital signal) is supplied variable, the output level of the on-screen signal can be adjusted by the current value.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the on-screen circuit of the present invention, FIG. 2 is a specific circuit diagram of the present embodiment, and FIGS. 3 (a), (b) and (c) show the present embodiment. It is a waveform diagram of the signal handled.

The present embodiment shown in FIG. 1 is different from the conventional example shown in FIG. 6 in that the independent terminal 22 to which the output level adjustment signal is inputted is removed, and the terminals 21a to 21a to which on-screen signals are inputted.
1c is replaced with the shared terminals 1a to 1c, and an on-screen signal is input to each of the terminals 1a to 1c via the circuit 50.

 Next, a more specific circuit will be described with reference to FIG.

In FIG. 2, only one of the R, B, and G3 channels is shown, but the other two channels are configured by the same circuit.

The common collector of the transistors 10 and 11 is connected to a power supply voltage supply terminal 17 (potential is V _CC ), and the common emitter is grounded via the resistor 4 and connected to the output terminal 19. The input of the current mirror constituted by the transistors 8, 9, 12, 13 is the collector of the transistor 7, and the output is grounded via the resistor 5 and the diodes 37, 38 and connected to the base of the transistor 11.
The base of the transistor 7 is grounded via the bias voltage source 14, and the emitter is connected to the variable resistor 3 and the emitter of the transistor 6 via the on-screen signal input and output level adjusting terminals 1a (1b, 1c). . A resistor 2 is connected to the other end of the variable resistor 3, and a bias voltage source VR1 is connected to the resistor 2. The collector of the transistor 40 is connected to a common connection point between the base of the transistor 10, the emitter of the transistor 32, and one end of the resistor 27.
It is connected to a common connection point between one end of the resistor 5 and the anode of the diode 37 via 39, and the emitter is grounded.

 Next, the operation of this embodiment will be described.

First, the operation when the state of the on-screen signal is at a low level will be described. In this case, the base of the transistor 6 becomes low level, and the transistor 6 is turned on in the differential switch composed of the transistors 6 and 7,
The transistor 7 turns off. Therefore, transistors 8, 9,
No current is supplied to the current mirror formed by the transistors 12 and 13, no current flows through the resistor 5, the diodes 37 and 38, and the bases of the transistors 11 and 40 are not biased. Accordingly, the transistors 11 and 40 are turned off, and the primary color signal input from the terminal 18a is output from the terminal 19a via the emitter follower including the transistor 32 and the resistor 27 and the emitter follower including the transistor 10 and the resistor 4.

Next, an operation when the state of the on-screen signal is at a high level will be described.

When the voltage of the bias voltage source 14 is set to a value lower than the high level of the on-screen signal, in the differential switch including the transistors 6 and 7, the transistor 7 is turned on, and the transistors 8, 9, 12, and 13 are turned on. Current is supplied to the current mirror composed of
Since a current flows through 8, the bases of the transistors 11, 40 are biased, and the transistors 11, 40 are turned on. When the transistor 40 is turned on, the base of the transistor 10 is almost at the ground potential, and the transistor 10 is turned off. As a result, the primary color signal input from the terminal 18a is
It is not output to 9a. In this case, the forward voltages of the diodes 37 and 38 are V _F37 and V _F38 , the voltage of the voltage source VR1 is V _R1 , and the voltage source 1 is
The potential of 4 is V ₁₄ , the resistance of resistors ₂ , ₃ , and ₅ is R ₂ , R ₃ , R ₅ , and the forward voltage between the base and emitter of transistors 7, 11 is V _BE7 , V
_{Assuming BE11} , the on-screen output level V _ON output to the terminal 19a (19b, 19c) is as follows.

In the equation (1), the on-screen output level V _ON can be adjusted by changing the resistance value R ₃ of the variable resistor 3. Accordingly, the waveforms of the on-screen signal, the primary color signal input to the terminals 16 and 18 and the output signal output from the terminal 19 are as shown in FIGS. 3 (a), 3 (b) and 3 (c).

As described above, in this circuit, the input and output level adjustment of the on-screen signal can be performed using only one terminal, that is, using only the terminals 1a (1b, 1c).

FIG. 4 is a circuit diagram of another embodiment of the on-screen circuit of the present invention, and FIG. 5 is a waveform diagram of signals handled in this embodiment.

In this embodiment, a sampling processing function is further added to the above-described embodiment. In this embodiment, a video signal processing circuit is provided.
The primary color signal input to the on-screen circuit 200 from 100 is subjected to a sampling process corresponding to the sampling signal input via the transistor 28 and the terminal 35, and then the ON signal input via the transistor 6 and the terminal 1a. The screen signal is inserted and output from terminals 19a to 19c. Also, terminals 1a-1c, 3
5 is also used as an output level adjustment of the on-screen signal and an output level of the sampling signal, and the output current of the on-screen signal and the sampling signal are adjusted by the control current supplied to the terminals 1a to 1c and 35. Perform The relationship among the primary color signal, the sampling signal, the on-screen signal, and the output signal is as shown in FIGS. 5 (a), (b), (c) and (d). This sampling signal is used to highlight the edges of the on-screen display. In this embodiment, since the input terminal of the on-screen signal and the output level adjustment terminal of the on-screen signal are also used in common, the input terminal of the extraction signal and the output level adjustment terminal of the extraction signal are also used in common. In this case, there is an advantage that a total of two terminals can be reduced.

The input of the current mirror constituted by the transistors 30 and 31 is connected to the collector of the transistor 29, the output is connected to the power supply terminal 17a via the resistor 26, and to the base of the transistor 33. The collector of transistor 29 is connected to the input of a current mirror consisting of transistors 30 and 31, and the base is
The emitter is connected to one end of the resistor 25 and the emitter of the transistor 28 via a terminal 35. The input of the current mirror constituted by the transistors 8, 9, 12, and 13 is connected to the collector of the transistor 7, and the output is grounded via the resistor 5 and connected to the base of the transistor 11. The collector of transistor 7 is connected to the input of a current mirror composed of transistors 8, 9, 12, and 13, the base is connected to ground potential via voltage source 14, and the emitter is connected to one end of resistor 3 via terminal 1a. 6 is connected to a common connection point with the emitters. The common emitters of the transistors 32 and 33 are connected to the power supply voltage supply terminal 17b via the resistor 27 and to the base of the transistor 10, and the common collector is grounded. The common collector of the transistors 10 and 11 is connected to the power supply terminal 17b, and the common emitter is grounded via the resistor 4 and connected to the output terminal 19a. Note that the voltages at the terminals 17a and 17b are at V _CC .

This embodiment is different from the above-described embodiment in that a function of adjusting the input and output levels of the sampling signal is added, but the method of inputting the sampling signal, the method of adjusting the output level, and the operation principle are the same as those of the case of the on-screen signal. Therefore, detailed description of the operation is omitted. The voltages of the voltage sources VR1 and VR2 are V _R1 and V _R2 , the potentials of the voltage sources ₁₄ and ₃₄ are V ₁₄ and V ₃₄ , and the resistances of the resistors ₂ , 3, ₅ , 24, 25 and 26 are R ₂ and R, respectively. ₃ , R ₅ , R ₂₄ , R ₂₅ , R ₂₆ and the potential of terminal 17
If V _CC is V _BE7 , V _BE10 , V _BE11 , V _BE29 , V _BE33 , the forward voltage between the base and emitter of transistors 7, 10, 11, ₂₉ , ₃₃ is V _BE7 , V _BE10 , V _BE29 , V _BE33 , the output level of the on-screen signal V _OS and the sampling signal The output level V _NT is as follows.

By changing the resistance R ₃ of the variable resistor 3 in the equation (2), the output level V _OS of the on-screen signal can be adjusted. In the equation (3), the resistance R ₂₅ of the variable resistor 25 can be adjusted.
It is possible to adjust the output level V _NT the sampling signal to change the. Therefore, the input and output level of the on-screen signal can be adjusted only by the terminal 1a (1b, 1c), and the terminal 35
The input and output levels of the sampling signal can be adjusted only by the above.

〔The invention's effect〕

As described above, the present invention provides a common use of an on-screen signal input terminal and an on-screen signal output level adjustment terminal, or a common use of a sampling signal input terminal and a sampling signal output level adjustment terminal. As a result, the number of IC terminals can be reduced, and there is an effect that miniaturization of ICs, cost reduction, and improvement of reliability can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the on-screen circuit of the present invention, FIG. 2 is a specific circuit diagram of the embodiment of FIG. 1, and FIG.
5A to 5C are waveform diagrams of signals handled in the embodiments of FIGS. 1 and 2, FIG. 4 is a specific circuit diagram of another embodiment of the on-screen circuit of the present invention, and FIG. FIG. 4 is a waveform diagram of signals handled in the embodiment of FIG. 4, and FIG. 6 is a block diagram of a conventional example. 1a to 1c: On-screen signal input terminal, 18a to 18c: Primary color signal input terminal, 19a to 19c: Output signal, 50: Current adjustment circuit, 100: Video signal processing circuit, 200: On-screen circuit , 2,4,5,24,27,29 ... resistor, 3,25 ... variable resistor, 6-13, 28-33 ... transistor, 17 (17a, 17b) ... power supply voltage input terminal, 37 , 38 …… Diode, V _CC …… Power supply voltage, VR1, VR3 …… Bias voltage source.

Claims (1)

(57) [Claims] An on-screen signal including information such as channel switching, volume switching, television / video switching, and the like in a television receiver and a primary color signal supplied from a video signal processing circuit are inputted, and the inputted ON signal is inputted. In an on-screen circuit capable of inserting a screen signal into a primary color signal and outputting the same, and adjusting the level of the inserted on-screen signal, switching on / off in response to a change in the voltage level of the input on-screen signal Means, when the switching means is turned on, a predetermined current is supplied via the switching means, and a current supply means capable of adjusting the current value of the predetermined current; and the on-screen signal is at a predetermined level, When the switching means is turned on and a predetermined current is supplied from the current supply means, On-screen circuit voltage is generated corresponding to the constant current, and having a means for inserting the generated voltage to the primary color signals.